The problem with a public cap table is that it amounts to a public salary database. Usually companies (and employees) don't want everyone to publicly know everyone else's salary. When people do jobs you don't understand (like marketing, for the tech crowd here), or are perceived as underperforming, removing all doubt about their compensation breeds contempt.

Anyway, even buffer doesn't publish enough information as they don't publish the "preference stack". Whether by design or an oversight is hard to say. And you can't really publish it as it will lead to difficulty recruiting as candidates get soured by the prospect that investor's real equity is better than their sweat equity.

Sure, VCs talk but (speaking as a not-VC) I doubt they are going to share cap tables and such. They are busy people. If you, as a VC, care, talk to the company yourself. Even if they would share peer-to-peer, you are not a VC so you are not going to be privy to this VC-public info.